A system for producing hydrogen including a methane pyrolysis reactor, a solid-gas separator, and a downstream unit. The system includes a hydrogen and nitrogen feed upstream of the reactor that includes a tube reactor, a catalyst, a frit, and a heating mechanism. The system includes a first and second pressure gauge. A process for producing hydrogen including feeding a hydrogen stream to activate a catalyst, feeding a methane feed to a methane pyrolysis reactor, monitoring a differential pressure, feeding a nitrogen stream to purge the catalyst, feeding the methane pyrolysis product stream to a solid-gas separator, recovering the solid carbon byproduct, feeding a gas mixture stream into a downstream unit and recovering the separated hydrogen. A process for producing hydrogen using methane pyrolysis reactors by concurrently operating at least one of the reactors in a reaction mode and at least one of the reactors in a regeneration mode.

An apparatus and process for oxidant formation can be configured to facilitate improved mixing of for formation of an oxidant. Embodiments can be configured so conduits having a relatively large aspect ratio (e.g., 1.5 to 5 or 1.5 to over 5) can be utilized for improved gas mixing even in situations in which the carrier gas is at a relatively low pressure. Embodiments can also facilitate low nitrogen oxide formation combustion. Some embodiments can additionally provide improved carbon capture.